Namaste Anubhav ji,
Shivaratri is the 14th (Chaturdashi) night. On the 13th (Trayodashi) full day fasting is recommended.

The period of 3 ghati (1 ghatika = 24 min.) prior to sunset on every month’s Trayodashi of Shuddha paksha, is known as Pradosh. The Deity worshipped on Pradosh is Shiva.
On Pradosh, Vrat is done. The fasting and sadhana is done for the whole day and meals are taken at night after worshipping Deity Shiva.
Abhishek is done on Shiva’s pindi till Pradosh is over.
Shiva’s few moments of deep meditation (samadhi) is called Pradosh period. This period is considered very beneficial for whosoever does worship of Shiva either knowingly or unknowingly.
Thus, Shivratri and Pradosh (which falls near Mahashivratri) are connected.